linux-kernel - Re: [PATCH 1/2] GPIO: Add driver for Zynq GPIO controller

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Date:	Mon, 31 Mar 2014 10:22:09 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Harini Katakam <harinikatakamlinux@...il.com>
Cc:	Alexandre Courbot <gnurou@...il.com>,
	Michal Simek <michal.simek@...inx.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Rob Landley <rob@...dley.net>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	michals@...inx.com, Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH 1/2] GPIO: Add driver for Zynq GPIO controller

On Sat, Mar 29, 2014 at 5:44 AM, Harini Katakam
<harinikatakamlinux@...il.com> wrote:
> On Sat, Mar 29, 2014 at 3:20 AM, Linus Walleij <linus.walleij@...aro.org> wrote:
>> On Thu, Mar 27, 2014 at 4:25 PM, Harini Katakam <harinik@...inx.com> wrote:

>>> +/* Read/Write access to the GPIO PS registers */
>>> +static inline u32 zynq_gpio_readreg(void __iomem *offset)
>>> +{
>>> +       return readl_relaxed(offset);
>>> +}
>>> +
>>> +static inline void zynq_gpio_writereg(void __iomem *offset, u32 val)
>>> +{
>>> +       writel_relaxed(val, offset);
>>> +}
>>
>> I think this is unnecessary and confusing indirection.
>> Just use the readl_relaxed/writel_relaxed functions directly in
>> the code.
>>
>
> This is just to be flexible.

Define exactly what you mean with "flexible" in this context. I
only see unnecessary overhead and hard-to-read code.

>> This is also pretty convoluted. Are you sure you don't want to
>> implement one gpiochip per bank instead? I guess the final "+1"
>> means there is actually one IRQ per bank even?
>
> There is only one IRQ for all four banks.

OK I get it. Then it makes sense to have all banks registered as
one device and the IRQ tied to this one device.

>>> +static const struct dev_pm_ops zynq_gpio_dev_pm_ops = {
>>> +       SET_SYSTEM_SLEEP_PM_OPS(zynq_gpio_suspend, zynq_gpio_resume)
>>> +       SET_RUNTIME_PM_OPS(zynq_gpio_runtime_suspend, zynq_gpio_runtime_resume,
>>> +                          zynq_gpio_idle)
>>> +};
>>
>> Is this runtime PM implementation aligned with Ulf Hansson's recent
>> new helpers to simplify suspend+runtime PM coexistance?
>>
>
> I'm sorry i just looked at them -
> pm_runtime_force_suspend/resume are not used here.

Sorry, I was more thinking of change
717e5d458e3bfca495a38dca61c64f274c049e46
"PM / Runtime: Implement the pm_generic_runtime functions for CONFIG_PM"

Yours,
Linus Walleij
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